I'm going to say it is to do with slavery and lynchings.
As for Loki saying context of how you said it doesn't matter if the person is offended that hardly makes sense if it isn't a racist remark but rather lost in cultural differences. Also what happens if a black person calls another ****** or if someone gets called a stupid white **** I can't see the same uproar occurring. I mean I've seen a certain footballer call others a ****** as a joke albeit not on the field, should they be banned for joking/having a laugh?
No it does make perfect sense as that is one of the ways racism works.
I was out with my boys yesterday at the Cinema and we were killing sometime, and we were having a laugh about something or nothing. I called him a cheeky Monkey. Entirely safe because
A) He is my Son
B) He is White
C) We were all laughing at the same thing.
What if he was from a mixed marriage and I called him a Cheeky Monkey in a more serious tone without laughing. To passers by the context could have changed. Slightly less safe ground
Here's another example, when I was in my late teens my group of mates were all straight 100% English and I was the one who was half Scottish (if such a thing exists, although my Dad used to tell me it was the better half, I tend to agree at times) So as you can imagine a group of lads who played football together, went on the beers together, went to college and Uni together we were a close bunch but within that group the language was coarse and I often got referred to as the Thistle Licker.
'Get a round of drinks in you tight arsed Scottish ****'. Was common
Likewise my mate was often called Wingnut as he had massive ears. We had an Irish lad who was pretty poor at football he often got ripped. Quite often you heard shouts of WTH was that you effin Spud Muncher' And so it went we all had a derogatory term for each other that was safe and ok within our own social group we defined the boundaries of what we could call each other.
If somebody called us something outside our own social group of that nature then it is less safe.
Which leads me onto when Black on Black call each other the N word. If it is defined within their social group to use that word then that's no issue. No outside pressure or influence will change that. That is how social groups work in society and have worked since we have been drawing on cave walls and picking our own arses.
Racism or discrimination is very easy to understand. It's the context of the words used and then the historical context of it's meaning that will quite often define how it is received. Thats why calling you a whitey will have not one iota of difference. The white social group has never been discriminated against. (Interesting to see if that changes over the next couple of hundred years). You call a black guy the N word then there is more social context to that due to how blacks were enslaved and discriminated against. All well and good saying oh they should get over it that was years ago. However as I mentioned above outside influences very rarely change the mechanics of what is and isn't acceptable to any social group.
Thats where the argument fails of I have black mates so I cant be racist but............... I have muslim mates so I cant be racist but..............
We can are and have all been guilty of discrimination be it actively or passively